|The diagram shows angle of view or angle of acceptance.|
I have been looking back through my college notes and came across this series of pictures. I used the colour film you find in the pound/ budget shops. I have had no problems with the way the film has performed.
These pictures show how much of the view in front of the lens is depicted at the negative. As the focal length of the lens increases the angle of view reduces but the object size gets bigger. Therefore as you go up the focal range so the depth of field lessens.
|View at 35mm|
|View at 50mm|
|View at 80mm|
|View at 135mm and the cold is getting to me.|
|View at 210mm|